CT colonography may increase colorectal cancer (CRC) screening rates as a more convenient and less invasive alternative to colonoscopy, according to a study published Oct. 21 in the American Journal of Roentgenology.
"Although colonoscopy is the preferred test for CRC screening and prevention, the invasiveness and inconvenience of colonoscopy are often cited as reasons for noncompliance with this form of screening," Fouad J. Moawad, MD, of the department of gastroenterology at the National Naval Medical Center (NNMC) in Bethesda, Md., and co-authors wrote.
As part of a process improvement initiative at NNMC, Moawad and colleagues sought to investigate whether the reduced invasiveness of CTC compared with colonoscopy could help improve suboptimal colorectal screening, which at present is only about 50 percent nationally, survey-based studies estimate.
Two hundred and fifty consecutive asymptomatic individuals chose to undergo free colorectal cancer screening using CTC as part of NNMC's Colon Health Initiative at NNMC. None of the self-selecting participants had ever received CTC scans, though 57 had previously undergone colonoscopy.
All patients were asked why they had chosen CTC and whether they would have undergone CRC screening if CTC had not been an option. Additionally, the 57 patients who had previously undergone colonoscopies were asked after CTC whether they preferred the CTC or colonoscopy exam.
The researchers found that the most common reason patients chose to receive CTC screening (cited by 34 percent of participants) was convenience. Because both CTC and colonoscopy required two to three week waiting periods prior to screening at NNMC, the authors interpreted this response as a result of CTC's speed and less invasive nature. The CTC exam takes substantially less time than colonoscopy to perform and does not require sedation, therefore allowing patients to continue their daily routines with relative ease, the authors noted.
The study also found that 37 percent of subjects said they would not have undergone CRC screening if CTC were not an option. Ninety-five percent of individuals who underwent both CTC and a previous colonoscopy responded that they preferred CTC. The authors acknowledged selection bias in this question, however, since the patients had voluntarily chosen CTC as an alternative to colonoscopy.
The second most common reason for undergoing CTC, indicated by 13 percent of respondents, was because of recommendations from primary physicians. The authors attributed this finding to growing acceptance and positive perceptions of CTC among physicians as an effective modality for CRC screening. Eleven percent of respondents cited the safety of CTC as their primary rationale for choosing CTC, as the invasiveness and sedation required by colonoscopy put patients with previous health concerns at higher risks for side effects. Nine percent of the sample reported choosing CTC because they expected a normal exam, and 8 percent responded that they had fears about colonoscopy.
"Perhaps the most important finding of our initiative was that more than one third of patients queried would not have undergone CRC screening if CTC had not been available as a screening option." Given the poor screening rates in the general population for colorectal cancer, which is the second leading cause of cancer mortality in the U.S., the authors found this response encouraging. Moreover, Moawad and colleagues reported that in the three years since CTC has been offered at NNMC, CRC screening has increased by 70 percent.
The authors expressed surprise at the 4.8 percent of respondents who indicated that they had selected CTC because of its ability to detect extracolonic findings, since some physicians will not recommend CTC as a primary method for screening compared with the standard colonoscopy. Participants gave these responses after having signed the CTC consent form, which state that CTC is not as accurate as colonoscopy for identifying polyps 5 mm or smaller.
In discussing the debate over the radiation dose emitted by CTC, the authors concluded that "on the basis of low doses of radiation delivered with CTC, the advanced age of patients undergoing the examination for screening purposes, the proven performance characteristics of the examination, and the prevalence and incidence of adenomas and CRC, the risk-benefit ratio favors CTC compared with no screening.